This invention relates to a dust-proof device for a mechanical seal which prevents a fluid from leakage through rotary shaft portions.
In the mechanical seal of the above-mentioned kind, a seating ring on the stationary side which receives therethrough a rotary shaft is generally brought into slidable contact with a follower ring which is rotated together with the above rotary shaft, thereby avoiding the leakage of fluid from the outside of the sliding contact portion to the inside thereof. In order to enhance the sealing effect of the sliding contact surfaces in the conventional prior art, it is quite important to investigate all the factors, especially the configurations of sliding contact surfaces, of both the rings which constitute the rotating sliding surfaces. Therefore, in connection with both the rings, a variety of proposals have hitherto been made. According to the investigations of the present inventors, the following fact has been found out. That is, in the case that the outside fluid of a mechanical seal is a gas, especially when the outside gas contains much dust like the mechanical seal of the compressor for an automobile cooler, it is quite important to keep off the dust contained in the outside gas from the sliding surfaces as well as to investigate with regard to the above-mentioned rings. In other words, the entering of dust into the space between sliding surfaces apparently reduces the sealing effect of the mechanical seal.